An active matrix driving device has been widely used as a driving device for a liquid crystal display panel, an OLED (Organic Light Emitting Diode), or other displays. The active matrix driving device adopts a semiconductor device in which thin film transistors (TFTs) made of amorphous silicon or polycrystalline silicon are arranged on a glass substrate.
In recent years, an active matrix driving device has adopted a semiconductor device in which a polycrystalline silicon integrated circuit is arranged on an insulating substrate such as a glass substrate. In this polycrystalline silicon integrated circuit, peripheral drivers are integrated by using the polycrystalline silicon.
The high fineness of a display device such as the liquid crystal display panel calls for high-performance of the active matrix driving device to be used.
Under the circumstances, a study has been made on the use of a semiconductor device adopting a single-crystal silicon integrated circuit, in the active matrix driving device. This is because the single-crystal silicon integrated circuit has higher performance than that of the polycrystalline silicon integrated circuit.
For example, a Japanese translation of unexamined PCT publication No. 7-503557/1995 (Tokuhyouhei 7-503557; Published on Apr. 13, 1995) discloses a method for forming a single-crystal silicon integrated circuit on an insulating substrate such as a glass substrate. In the method disclosed in the published Japanese translation of PCT application, an integrated circuit (a single-crystal silicon layer) is formed on a silicon substrate, prior to bonding the integrated circuit with the insulating substrate via an adhesive agent.
Apart from the method in which the adhesive agent is used for bonding the insulating substrate with the single-crystal silicon integrated circuit, which is preliminary formed, there is another method for forming the single-crystal integrated circuit on the insulating substrate. In the other method, a silicon substrate is bonded with the insulating substrate, and then a thinning process is carried out to form an SOI (Silicon On Insulator) configuration.
Examples of the semiconductor device utilizing the SOI configuration are disclosed in Japanese Patents No. 2743391 (issued on Feb. 6, 1998), No. 3141486 (issued on Dec. 22, 2000), and No. 3278944 (issued on Feb. 22, 2002).
For example, unexamined patent publication No. 5-211128/1993 (Tokukaihei 5-211128; published on Aug. 20, 1993) discloses a method for fabricating the SOI configuration called Smart Cut method. By utilizing the Smart Cut method, it is possible to bond the single-crystal silicon with the insulating substrate, without the adhesive agent.
Namely, in the Smart Cut method, hydrogen ions having a predetermined concentration are implanted into a silicon substrate so as to have a predetermined implanted depth. This silicon substrate is bonded with an insulating substrate serving as a handling wafer. Then, the single-crystal silicon layer is separated by annealing from the silicon substrate at a portion where hydrogen ions are implanted, thereby forming the SOI configuration.
By forming a single-crystal silicon integrated circuit on the single-crystal silicon layer separated from the silicon substrate based on the process described above, a semiconductor device in which the single-crystal silicon integrated circuit is formed on the insulating substrate.
However, in cases where the single-crystal silicon integrated circuit is bonded with the insulating substrate via the adhesive, heat resistance causes a problem. More specifically, for example, after the insulating substrate is bonded with the single-crystal silicon integrated circuit via the adhesive agent, it is not possible to carry out a process requiring heat treatment or a process of forming a high quality inorganic insulating film or a TFT with respect to the insulating substrate. Thus, restrictions occur on a fabrication process and/or a device configuration.
Unlike the method in which the adhesive agent is used for the bonding, according to the method in which the single-crystal silicon integrated circuit is formed on the insulating substrate, the restrictions do not occur on the fabrication process and/or the device configuration. This is because the single-crystal silicon layer (the layer to become the single-crystal silicon integrated circuit) is formed on the insulating substrate without the adhesive agent, like in a method such as the Smart Cut method. Instead, the following problem occurs.
In the Smart Cut method, the hydrogen ions are implanted into the silicon substrate, so that the single-crystal silicon layer is formed. Note that the hydrogen ions may be implanted into an active region, in which a field effect transistor (FET) or other devices are formed, in the single-crystal silicon layer. This causes the active region to be damaged. When the active region is damaged by the implantation of the hydrogen ions, the problem occurs that it is not possible to fully demonstrate the performance of an element such as the field effect transistor.